As is well known in the art, hexamethylene diamine is used extensively in the production of nylon 66. One well-known and commercially applied method of producing hexamethylene diamine is via the hydrogenation of adiponitrile. The various commercial producers utilizing this process do utilize a variety of different raw materials in arriving at adiponitrile. In one method known in the art, cyclohexane is converted to adipic acid which is then converted to adiponitrile by passing adipic acid vapor mixed with ammonia over a dehydrating catalyst. Characteristic of this type of process is that described in British Pat. No. 568,941.
In yet another commercial process, butadiene is chlorinated to dichlorobutenes which are cyanated to dicyanatobutenes, which upon reduction yield adiponitrile. Alternatively, the butadiene may be cyanated directly to yield dicyanatobutenes. Finally, adiponitrile has been produced via an electrolytic process (see, e.g., U.S. Pat. Nos. 3,193,476, 3,193,477, and 3,193,481, and Belgian Pat. No. 649,625).
As is readily apparent, depending upon the process used to make the adiponitrile, the reaction mixture of the hydrogenated product will vary in composition. In general, regardless of the initial process chosen, the hexamethylene diamine is distilled off from the reaction mixture leaving a distillation residue, which among other materials may contain hexamethylene diamine, adiponitrile, bis(hexamethylene) triamine, 1,4-di(aminomethyl)-1-ethylcyclohexane, poly(hexamethylene) polyamines, and small amounts of water, perhaps present by adsorption from the air and the like.
Because the composition of the distillation residue will vary widely from process-to-process and even from batch-to-batch, the distillation residues have found very limited use. To date, they have found limited use in the production of asphalt anti-stripping agents and as curing agents for epoxy resins.